The present invention relates to portable multiple pair cable test apparatus and more particularly to a portable self-contained automatically sequencing test set for confirming the continuity and detecting shorts, crosses and reverses between any of the pairs of a multiple pair cable.
Complex telephone and communications systems have proliferated and with the introduction of such systems, such as multiple line telephone sets, communications cables of many wire pairs have been required in order to connect each telephone set with centrally located power supplies, signal indicator units, intercom modules and other sets. Telephone set cables typically include at least 25 wire pairs, and often many more pairs within the cable. A typical installation of communications cable includes interconnections through many terminal blocks and connectors before establishing paths between each telephone set, the telephone equipment room, and the central office equipment. In such installations there are many opportunities for dis-continuities to occur within the cable. For instance, the cable section may contain factory defects, or the installer may have made errors in connection causing the pairs to be terminated at the wrong terminals and connectors, or to be shorted or to be crossed or to be opened.
A standard practice followed in the telephone industry has been to provide telephone connection cables with preinstalled connection plugs at one end thereof. The plugs have been installed and tested in the factory and are generally reliable. The disadvantage of this practice has been that the cables have been of predetermined length necessarily always in excess of the length of cable required for any given installation. Thus, the cable has been cut at the other end, resulting in wasted cable. A recent development to overcome this waste has been to provide installers with tools for installing connectors in the field. Where this practice is employed, cable may be cut to precise length, and connectors are then applied with the aid of tools such as the Field Assembly Solderless Termination (FAST) tool made by the Amphenol Industrial Division of Bunker Ramo, Inc. Because of human errors and adverse working conditions the quality control and circuit reliability of such field-installed connectors may not be as high as the quality of the factory installed connectors.
A need has therefore arisen for rapidly checking the integrity of communication cables in the field, particularly inside office buildings, point to point cables, house cables, riser cables, cables between the telephone room and the telephone set location, cables between various PBX, PABX etc. components, cables between various parts of computer installations, cables between the various frames, racks or bays of telephone equipment, installed or uninstalled, cables between permanent or temporary racks, inside or outside the telephone central office installation, etc.
The standard testing procedure followed in the past, having drawbacks overcome by the present invention, involves manually placing a test signal on each pair of the cable at one end in sequence and identifing the pair at the other by manually searching for the pair with the signal on it. Such a slow procedure often requires many hours, days or even weeks for testing cables having multiple pairs in large installations. In addition, the possibilities of human error in such a testing routine are significant and, at least two technicians are required to perform such tests. In addition, miswires and crossed wires and shorts to other wire pairs have often gone undetected. All of these foregoing limitations are overcome by the present invention.
It is therefore an object of the present invention to provide a multiple pair cable test set that automatically tests each wire pair in the cable for continuity and correct connection, and that stops the test sequence automatically upon the detection of a dis-continuity, short, or other incorrect interconnection of a wire pair undergoing testing.
Another object of the present invention is to provide a cable test set with a display that gives a visual identification of a wire pair having a dis-continuity or misconnection.
A further object of the invention is to provide a multiple pair cable test set which is fully self contained and portable, that does not require special cabling or interconnection and that may be rapidly connected to installed cables, and that may be operated by a single operator to provide an accurate and comprehensive test of cable pairs.